The invention relates to an apparatus for use in manufacturing ophthalmic components, such as contact lenses, and more particularly, to an apparatus for cleaning the molds used to form contact lenses.
The manufacture of ophthalmic components, for example contact lenses, is typically carried out in a large number of separate production steps. Very often these production steps must be carried out in an ultra-clean (i.e., inert and sterile) environment such as a xe2x80x9cclean roomxe2x80x9d. Each production step, for example the manufacture and transfer of intermediate components, the positioning of equipment, such as molds, or the operation of equipment, presents an opportunity for contamination of the ophthalmic component. The danger for contamination is especially acute in the manufacture of contact lenses. If the lens manufacturing process is contaminated or corrupted in any way, in most cases the finished lens must be discarded.
Contact lenses are generally manufactured in automated or semi-automated production processes. Lens molds consisting of base curve (convex) and front curve (concave) mold halves are transported on carriers through the production process. The molds are symmetrical and are fitted together to form a small crescent shaped mold cavity between the base curve and front curve molds. A lens is formed by introducing a monomer in the front curve mold and then sandwiching the monomer between the base curve and front curve molds. The monomer is then polymerized through heat treatment, light treatment or other polymerizing process, thus forming a lens. The lens is then removed from the molds for further treatment and is packaged for consumer use.
If either the base curve or front curve mold is contaminated in any way, the lens formed will contain a flaw, such as an uneven face, and will most likely have to be discarded. Therefore, great care is taken to clean the base curve and front curve molds prior to introducing the monomer to the front curve mold. Currently, the cleaning of the base curve and front curve molds is accomplished manually. Using a hand held compressed gas (i.e. nitrogen) gun, compressed gas is blown over the mold halves to remove any debris that may be present on the surface of the molds.
Manual cleaning is an inefficient method by which to clean equipment used in the manufacture of ophthalmic components, especially contact lens molds. Given that the majority of the manufacturing steps involved in the production of contact lenses are automated, the use of any manual cleaning method has the potential to damage equipment, reduce the quality of finished product or at a minimum reduce the efficiency of the overall manufacturing process. For example, lens molds typically travel through the contact lens manufacturing process on carriers which are designed to hold the molds securely throughout the process. If the lens molds are manually cleaned, they are susceptible to becoming misaligned in their carriers or contaminated through inadvertent human contact. A misaligned mold half could form a misaligned lens mold. Misaligned molds result in flawed contact lenses or in manufacturing downtime to either remove or repair the misaligned mold. Similarly, as a result of fatigue or inattention, a technician could inadvertently permit a contaminated mold to proceed through the contact lens manufacturing process, thus resulting in a defective contact lens that could be sold to consumers.
The need therefore exists for providing an apparatus for use in the manufacture of ophthalmic components, especially contact lenses, that cleans a desired intermediate component or part to prevent contamination of that part, yet overcomes the above-described disadvantages of manual cleaning methods. In particular, the novel apparatus permits the cleaning of contact lens molds to occur automatically, uniformly and concurrently with other manufacturing steps. The apparatus of the present invention allows for continuous operation, and thus makes more extensive automation of the manufacturing operation possible.
It is an object of this invention to provide an apparatus and method for cleaning ophthalmic devices, especially contact lens molds.
It is a further object of this invention to provide an apparatus to automate the cleaning of ophthalmic devices, especially contact lens molds.
It is a further object of this invention to provide an automated apparatus and method for the cleaning of contact lens molds that increases the efficiency of the contact lens manufacturing process.
All of the above and other objects are achieved by an apparatus for the cleaning of ophthalmic components, especially contact lens molds. In its simplest form, the apparatus includes an ophthalmic component carrier, a conveying means, such as a conveyor, for transporting the carrier, and a cleaning station to receive and clean the ophthalmic devices. The cleaning station includes at least one cleaning assembly that is mechanically lowered onto the top of the lens mold carrier. There are recesses formed in the cleaning assembly such that when the cleaning assembly is lowered the recesses and the carrier define a substantially enclosed cavity in which a lens mold is housed. Compressed gas is then injected into the cavity to dislodge any debris that may be on the lens mold. The cavity is subjected to a vacuum to remove any debris that may be present.
In a preferred embodiment, the apparatus includes at least one front curve lens mold carrier and at least one base curve lens mold carrier. The front curve lens mold carrier includes a front curve top plate and a front curve bottom plate attached to the top plate. The front curve bottom plate has a plurality of holes and receiving slots formed therein. The receiving slots engage receiving members (e.g. pins) located on the base curve mold to stabilize the mold during monomer polymerization. The front curve top plate also has a plurality of holes formed therein. The top plate holes are in axial alignment with the bottom plate holes thereby providing an opening completely through the carrier when the top plate and the bottom plate are connected to each other. The top plate hole is separated into two sections by a flange. A hollow piston, guided by the flange, travels up and down in the two sections of the top plate hole. The piston is supported by a spring housed in the second section of the top plate hole which rests upon the top surface of the bottom plate. The top plate also has two top plate receiving slots in axial alignment with the bottom plate receiving slots.
The preferred embodiment of the apparatus further includes at least one base curve lens mold carrier. The base curve lens mold carrier also has a plurality of holes formed therein. The holes formed in the base curve lens mold carrier are divided into a first (or top) section and a second (or bottom) section with the first section being larger in diameter than the second section. The base curve lens mold carrier also has a channel extending from the edge of the first section to the edge of the carrier which provides rotational alignment for the molds by engaging with a protrusion on the outer diameter of the mold flange. The base curve lens mold carrier also includes two raised receiving members (e.g. pins) which are in axial alignment with the receiving slots formed in the front curve lens mold carrier and which engage with the receiving slots to form a stable mold for manufacturing a contact lens. Preferably, the carriers are transported to the cleaning station on a conventional conveyor.
The cleaning station which receives the front curve and base curve lens mold carriers is essentially table-like and includes at least two cleaning assemblies suspended from the underside of the table that can be lowered onto the top of the lens mold carriers. Preferably, the cleaning station consists of four legs and two parallel cross support members attached to the upper portion of the legs. A mounting plate (the table top) is movably attached to both cross support members in a manner that allows the mounting plate to move (i.e. slide) in relation to the cross support members. At least two means for providing vertical movement, such as pneumatic cylinders, are attached to the bottom surface of the mounting plate. At least two connectors for connecting the lens mold cleaning assemblies to the pneumatic cylinders are attached to the bottom of the pneumatic cylinders.
At least one front curve lens mold cleaning assembly and one base curve lens mold cleaning assembly are attached to the connectors. Each of the cleaning assemblies includes a top plate, a middle plate, and a bottom plate. The bottom plate of each assembly has a number of recesses corresponding to the number of lens molds carried on the lens mold carrier. The bottom plate recesses are also formed such that they can be in axial alignment with the holes of each carrier.
Each of the top, middle and bottom plates has a plurality of holes and recesses arranged to form two channels of fluid communication through the cleaning assembly. In operation, the first channel allows compressed gas to flow through the assembly to be injected into the recesses formed in the bottom plate. The injected gas dislodges any debris that may be present on the lens molds. The second channel of fluid communication allows an external vacuum source to pull the gas and debris out of the recesses.
After the front curve and base curve lens molds are cleaned, the cleaning assemblies retract and the conveyor carries the lens mold carriers to subsequent stations in the contact lens manufacturing process.